There is a need, in particular for enhanced emergency services (911 in the US, 112 in Europe) to provide a geographical localization information about the device from where an emergency call has been initiated. For devices connected to a Local Area Network LAN, like an Internet Protocol IP based telecommunications terminal e.g. an IP phone, or IP wireless base station, there exists specific protocol like Simple Network Management Protocol SNMP to centralize some information about that devices. Usually, some data collection mechanism about all the network devices will run on some management. An update of any change of some status of these devices on the network can be obtained. The type of information a device can provide to the management will depend on the Management Information Bases MIB that are supported by that device.
A device supports a MIB if the device is capable of supplying the type of information defined in the objects specified in the MIB. Most devices can provide the type information defined in the objects specified in certain standard MIBs, known as MIB I and MIB II. The format and layout of MIB II is specified in Request for Comments RFC 1213. Additional standard MIBs have been defined for information types not covered in MIB I and MIB II, and new MIBs are being developed on an ongoing basis. However, support for these standard MIBs varies from device to device. A device may only support a subset of their own proprietary MIBs, and many devices operate in more than one mode.
In U.S. Pat. No. 6,122,639 is disclosed a method of collecting information about a device in a network for storage in a database. It is based on a regular mapping of some device type identifier to a plurality of information sets associated with that identifier. It implies a transfer of a non negligible amount of data particularly in nowadays LAN to which a high number of devices like IP telecommunications terminal will be connected.
In U.S. Pat. No. 5,982,753 is disclosed a test instrument for testing a LAN. This test instrument once connected to that LAN, will conduct a segment discovery test in which the network devices are analyzed to detect local hosts, switches, routers, bridges and other devices, and further determine addressing information such as IP addresses, MAC addresses. A data base of these addresses of the various devices can be compiled. The type of reports chosen depend on the contents of the set of available MIBs as well as the particular ports selected for analysis. A switch typically has ports as listed according to the bridge MIB and also has interfaces which correspond to ports but may also include the backplane and SNMP agents. If the bridge MIB is available from the switch, the test instrument can obtain a list of MAC addresses of devices attached to any port. These MAC addresses are then matched by port against the data base to obtain the report of IP and MAC addresses and device names by port.
But this method cannot be applied for emergency application concerning telecommunications terminals like IP phones since MAC address does not provide any information about the physical port usually RJ45 plug to which they are connected to that LAN. And a localization of a device will only be possible if to each MAC addresses of a device connected to the LAN can be affected with certainty a corresponding valid port number. This problem appears to be crucial in this context since the user of telecommunications terminals to be connected to a LAN will be even encourage to relocate its device according to its need anywhere over the LAN infrastructure. Such advantage of the use of e.g. an IP phone will be to much restricted if it is contingent by some specific registration each time such telecommunications terminal is relocated over the LAN.